Designers may increase performance of processors and integrated circuit devices by improving their internal algorithms or methods of executing instructions. In many cases, improving the execution of instructions requires increasing the number of components in those devices, such as transistors, resistors, etc. Today it is not uncommon to have complex integrated circuit devices, such as processors or application specific integrated circuits, which contain millions, even billions, of transistors. Additionally, designers may increase performance of processors and integrated circuit devices by increasing the operating frequencies. These increased operating frequencies, the coupled with increasingly larger and larger numbers of components in such devices, have created numerous problems.
One problem related to these increased operating frequencies and integrated circuit devices with millions of transistors is a phenomena referred to as step load. Operating integrated circuit devices that have millions of switching devices at high frequencies tends to rapidly change the amount of operating current and power consumption of the devices. For example, modern processors may see rapid increases in processor power demands that approach 100 amps in fewer than 10 clock cycles, when the demands are not controlled. This step change in power consumption load, sometimes referred to as “di/dt”, is the difference between maximum and minimum power consumption of the system within a specified time interval. For a system to operate correctly, the power supply must be capable of maintaining voltage levels within a tight tolerance. If power consumption of the system varies widely over a short period of time, this power variation complicates power distribution which in turn increases the total cost of the system.
A large change in current over a very small amount of time will cause the power supply to droop or spike. This can cause issues both with timing (primarily slowing the circuits down in response to a voltage droop), as well as will both VccMin and VccMax issues (circuit operability). Excessive step loads lead to large frequency and voltage guard bands. As circuits become increasingly dense, with higher numbers of switching devices and even more operating units or processor cores on a single circuit die, this problem of step load will only become worse.